When filtering is to take place from the inside out, the rotor shaft has a hollow core and liquid to be filtered is fed to the inside of the rotor shaft. The filter element and the rotor shaft have suitable openings through which the liquid to be filtered is fed to the inside of the filter element. The filtering takes place from the inside of the filter element and out though the filter cloth. Particles in the liquid are separated on the inside of the filter cloth.
A plurality of filter elements is attached to the rotor shaft around the periphery thereof, together forming filter discs. The rotor shaft is usually capable of carrying a plurality of such discs.
During operation, the rotor shaft carrying the filter discs is rotated and the filter discs are partially immersed in filtered liquid during rotation. The liquid level inside the filter discs is higher than the liquid level outside the filter discs. Particles separated on the inside of the filter cloth are rinsed away with the help of spray nozzles placed so that the jets of liquid from the nozzles hit the outside of the filter cloth when the filter cloth is in the air. The particles are rinsed away and flow through the filter element and into the rotor shaft, where they are caught in a reject trough.
The filter element according to the present invention can also be used in disc filters for filtering from the outside of the filter discs and into the rotor shaft, wherein particles are deposited on the outside of the filter cloth and the filtered liquid flows into the rotor shaft. A reject trough can be arranged on the outside of the filter discs to catch reject that has been rinsed away, so that this can be rinsed down and “creamed off”.
Usually known filter elements consist of a framework or structure over which a bag of filter cloth is treaded and crimped, or a framework and replaceable panels of filter cloth. The basic thought is that the framework is reused.